I suggest that you read Jerre Mangione and Ben Morreale's La Storia: Five Centuries of the Italian American Experience. Although it covers a large time period, the book's heart and soul are the chapters detailing why so many Italians departed their homes, the conditions they found here, and how they so nobly overcame them. It's my grandparents' and great grandparents' magnificent story; a story of love, courage, sacrifice, hard work, values, faith, family and friends. And it's our story and we must never forget it nor let our children and grandchildren forget it.
"There are only two lasting bequests we can give our children - one is roots, and the other, wings." -- Hodding S. Carter
"You live as long as you are remembered." -- Russian proverb
Also interesting, but in Italian, is the movie produced in 2007 called Golden Door. Although not a documentary, it really gives you a sense about what it was like for our ancestors to leave some of their Italian towns. The person in the movie emigrated from rural Sicily.
I too saw the film on two occasions and unfortunately it was not popularized by the liberal press as a must see movie since it reflected poorly upon the illegal aliens arriving currently, illegally and arrogantly into the USA with demands no less!! =Peter=
PS- As it turns out P. D'Angelo is from a town very close to where some of my people are from (he was from Introdaqua in Abruzzo). This book gives me a taste of what my people may have experienced - like you can go back in time and walk in their **SPAM**.